JPS59185005A - Multi-channel reproducing circuit - Google Patents

Abstract

PURPOSE:To decrease remarkably power consumption by forming a current source of a magnetoresistance effect head and a current of each amplifier circuit with one circuit's share. CONSTITUTION:The circuit consists of n-set differential amplifier circuits 7, 8, 9 whose power terminals are connected in series between a voltage source 10 and ground and n-set of magnetoresistance effect heads 2, 4, 6 picking up a signal depending on the change in a constant current source 1 and a resistor connected in series with the constant current source, and capacitors 11, 12 are connected between each high voltage and each low voltage terminals from the 2nd amplifier circuit 8 to the n-th amplifier circuit 9. On the other hand, both terminals of the magnetoresistance effect heads 2, 4, 6 are connected to differential input terminals of the amplifier circuits 7, 8, 9 respectively via capacitors 13-17. The unbalance of the current generated in the amplifier circuits 7-9 in accordance with the amplitude of the inputted signal is absorbed by capacitors 11-12 inserted between voltage source terminals of each amplifier circuit, allowing to reduce remarkably the power consumption due to the differential amplifier circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application) The present invention relates to a multi-channel reproduction circuit suitable for power saving.

(Background) Figure 1 shows an example of a multichannel reproduction circuit using a magnetoresistive head. In FIG. 1, respective magnetoresistive heads 2, 4.6iζ constant current sources 1, 3.5 are connected, and each connection point between these magnetoresistive heads and a constant current source has a The input sides of amplifiers 7, 8.9 are connected.

Generally, the resistance of a magnetic effect head is small, and the rate of change in resistance is also very small (approximately 1%).

Therefore, the current of the constant current sources 1 and 3.5 is approximately 10 mA to
It is necessary to flow 20mA. Therefore, a circuit using constant current sources equal to the number of channels, such as the conventional example shown in FIG. 1, has the disadvantage that the power consumed by these constant current sources becomes large.

In addition, since the rate of resistance change of the magnetoresistive head is small,
The signal voltage appearing on the magnetoresistive head 2, 4.6 is on the order of several hundred μV. Therefore, the amplifier circuits 7, 8 .
9 has a small dynamic range. However, in the conventional circuit shown in Fig. 1, is the amplifier circuit? .

(Objective) An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide power saving of a multi-channel reproduction circuit.

(Overview) The features of the present invention include n differential amplifier circuits (where n is an integer of 2 or more) in which type temperature terminals are connected in series between a voltage source and ground, a constant 7a current source, and a constant 7a current source. n means for picking up a signal by changing a resistance connected in series with a current source; n means for picking up a signal by changing the resistance; means for connecting terminals at both ends, and at least a high voltage body of the differential amplifier circuit other than the first differential amplifier circuit connected to the voltage source;
The present invention is characterized in that it has a quantity ' and B connected between the low voltage side power supply terminals.

(Example) Hereinafter, one embodiment of the present invention will be explained with reference to FIG. Second
In the figures, the same or equivalent parts as in FIG. 1 are designated by the same reference numerals.

First, the configuration of this embodiment will be explained. One end of the constant current source 1 is connected to a voltage source 10, and the other end is connected to one terminal of the first magnetoresistive head 2. The other end of the first magnetoresistive head 2 is connected to one terminal of a second magnetoresistive head. Thereafter, they are similarly connected in series up to the nth magnetoresistive head 6, and the other end of the nth magnetoresistive head 6 is grounded.

Next, amplifier circuits 7 to 9 are also connected in the same manner as above.

That is, the high voltage side voltage terminal of the first amplifier circuit 7 is connected to the voltage source 10, and the low voltage side voltage terminal is connected to the high voltage side voltage terminal of the second amplifier circuit 8. The second amplifier circuit 8
The low voltage (111! voltage terminal) is connected to the high voltage side voltage terminal of the third square box amplifier circuit, and the following amplifier circuits are connected in series in the same way.Then, the low voltage side voltage terminal of the nth amplifier circuit 9 is Grounded.

Moreover, the second amplifier circuit 8 to the n-th amplifier circuit 9
A capacitor is connected between each high voltage and low voltage terminal. On the other hand, the respective differential input terminals of the amplifier circuits 7, 8.9 are connected to the corresponding magnetoresistive heads 2, 4.
．． Both terminals of 6 are connected via capacitors 13 to 17, respectively.

Next, the operation of this embodiment will be explained. A current of, for example, 10 mA is supplied from a constant current source 1 to n magnetoresistive heads 2 to 6 connected in series. For this reason,
When the magnetoresistive heads 2 to 6 pick up signals from a magnetic tape (not shown), the picked up signals are sent to the amplifier circuits via capacitors 13 to 17 connected to the input terminals of each of the amplifier circuits 7 to 9. Enter each of 7 to 9. Each of the amplifier circuits 7 to 9 amplifies the input signal and outputs the amplified signal from its respective output terminal.

At this time, the amplifier circuit 7
The unbalance of the current generated at points 9 to 9 is absorbed by each section 11 to 12 inserted between the voltage source terminals of each amplifier circuit.

For example, when the alternating current (signal current) flowing through the first amplifier circuit 7 is large and the alternating current flowing through the second amplifier circuit 8 is small, a charge proportional to the difference in current is accumulated in the capacitor 11. Ru. Conversely, when the alternating current flowing through the second amplifying circuit 8 is large, the current supplied from the first amplifying circuit 7 is small, and the difference in current is applied to the capacitor 11.
Supplied from. In this way, the currents of each amplifier circuit are always kept balanced, and stable operation is performed.

According to this embodiment, there are n magnetoresistive heads.

Since both ends of each of 2 to 6 are connected to the two input terminals of the differential amplifier circuit in the subsequent stage, the differential amplifier circuit can accurately amplify the signal generated by the corresponding magnetoresistive head. .

Further, since current is supplied to n magnetoresistive heads from one constant current source, power consumption by the constant current source is reduced to 1/n of that of the conventional device described above. Furthermore, since power is supplied from one voltage source 10 to the n differential amplifier circuits 7 to 9, power consumption by the differential amplifier circuits can be significantly reduced.

Although the above embodiments have been described using a magnetoresistive head as an example of the input means, the present invention is not limited thereto, and any input means lζ can be applied.

(Effects) As described above, according to the present invention, the current source of the magnetoresistive head and the current of each amplifier circuit can be configured by one circuit. Therefore, power consumption can be significantly reduced, which is very effective for circuits that require a multi-channel configuration.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of a conventional multi-channel reproducing circuit using a magnetoresistive head, and FIG. 2 is a circuit diagram of an embodiment of the present invention. 1.3.5...Constant current source, 2,4.6...Magnetoresistive head, ? , 8.9...Differential amplifier circuit, 1
1.12...Michihito Hiraki, patent attorney representing capacitors

Claims (1)

[Claims] (N differential amplifier circuits in which power terminals are connected in series between a 1111 pressure source and ground (n is an integer of 2 or more);
a constant current source, n means for picking up a signal by changing a resistance connected in series with the constant current source, and picking up a signal by changing the resistance in each of the n differential amplifier circuits. means for connecting the terminals at both ends of each of the n means, and between the high voltage side and low voltage side power supply terminals of the differential amplifier circuits excluding at least the first differential amplifier circuit connected to the voltage source; A multi-channel reproducing circuit characterized by having connected capacitors. (2) A patented circuit characterized in that the means for picking up a signal by a change in resistance is a magnetoresistive element.